package org.apache.velocity.runtime.resource;

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.    
 */

import java.util.Collections;
import java.util.Iterator;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

import org.apache.commons.collections.map.LRUMap;
import org.apache.velocity.runtime.RuntimeConstants;
import org.apache.velocity.runtime.RuntimeServices;

/**
 * Default implementation of the resource cache for the default ResourceManager.
 * The cache uses a <i>least recently used</i> (LRU) algorithm, with a maximum
 * size specified via the <code>resource.manager.cache.size</code> property
 * (idenfied by the
 * {@link org.apache.velocity.runtime.RuntimeConstants#RESOURCE_MANAGER_DEFAULTCACHE_SIZE}
 * constant). This property get be set to <code>0</code> or less for a greedy,
 * unbounded cache (the behavior from pre-v1.5).
 * 
 * @author <a href="mailto:geirm@apache.org">Geir Magnusson Jr.</a>
 * @author <a href="mailto:dlr@finemaltcoding.com">Daniel Rall</a>
 * @version $Id: ResourceCacheImpl.java 898032 2010-01-11 19:51:03Z nbubna $
 */
public class ResourceCacheImpl implements ResourceCache {
	/**
	 * Cache storage, assumed to be thread-safe.
	 */
	protected Map<Object, Resource> cache = new ConcurrentHashMap<>(512, 0.5f, 30);// MapFactory.create(512, 0.5f, 30, false);

	/**
	 * Runtime services, generally initialized by the <code>initialize()</code>
	 * method.
	 */
	protected RuntimeServices rsvc = null;

	/**
	 * @see org.apache.velocity.runtime.resource.ResourceCache#initialize(org.apache.velocity.runtime.RuntimeServices)
	 */
	public void initialize(RuntimeServices rs) {
		rsvc = rs;

		int maxSize = rsvc.getInt(RuntimeConstants.RESOURCE_MANAGER_DEFAULTCACHE_SIZE, 89);
		if (maxSize > 0) {
			// Create a whole new Map here to avoid hanging on to a
			// handle to the unsynch'd LRUMap for our lifetime.
			@SuppressWarnings("unchecked")
			Map<Object, Resource> lruCache = Collections.synchronizedMap(new LRUMap(maxSize));
			lruCache.putAll(cache);
			cache = lruCache;
		}
		rsvc.getLog().debug("ResourceCache: initialized (" + this.getClass() + ") with " + cache.getClass() + " cache map.");
	}

	/**
	 * @see org.apache.velocity.runtime.resource.ResourceCache#get(java.lang.Object)
	 */
	public Resource get(Object key) {
		return cache.get(key);
	}

	/**
	 * @see org.apache.velocity.runtime.resource.ResourceCache#put(java.lang.Object,
	 *      org.apache.velocity.runtime.resource.Resource)
	 */
	public Resource put(Object key, Resource value) {
		return cache.put(key, value);
	}

	/**
	 * @see org.apache.velocity.runtime.resource.ResourceCache#remove(java.lang.Object)
	 */
	public Resource remove(Object key) {
		return cache.remove(key);
	}

	/**
	 * @see org.apache.velocity.runtime.resource.ResourceCache#enumerateKeys()
	 */
	public Iterator<Object> enumerateKeys() {
		return cache.keySet().iterator();
	}
}
